Water Research 38 (2004) 3155–3166 Routine monitoring of antibiotics in water and wastewater with a radioimmunoassay technique Shinwoo Yang, Kenneth Carlson* Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523-1372, USA Received 7 April 2003; received in revised form 27 April 2004; accepted 29 April 2004 Abstract Antibiotics are one of a group of pharmaceutical compounds that have been found in lakes and streams throughout the world and the occurrence of these compounds in the environment has raised concerns regarding the toxicity to aquatic organisms and the emergence of strains of antibiotic-resistant bacteria. The objective of this study was to assess the use of a relatively simple coupled solid-phase extraction (SPE)/radioimmunoassay (RIA) method for screening and/ or monitoring tetracycline (TC) and sulfonamide (SA) compounds in water. Cross-reactivity of TCs and SAs was used to determine the specificity of the assays. The results indicate that TC, oxytetracycline (OTC), chlortetracycline (CTC) of the investigated 5 TCs, and sulfamethazine (SMT), sulfamethoxazole (SMX), sulfadimethoxane (SDM) and sulfathiazole (STZ) of the investigated 6 SAs in water matrix cross-react to a similar degree within each family in RIA and SPE/RIA. Water samples were collected across a watershed in northern Colorado in addition to the influent and effluent of a wastewater treatment plant. SPE/RIA analysis of these samples was compared with SPE/liquid chromatography (LC)-mass spectrometry (MS) quantification of 5 TC and 6 SA compounds. Results of the study indicate that SPE/RIA can be an effective technique for monitoring antibiotic compounds in waters suspected to be contaminated with these compounds. The coupled method provides a sufficiently low detection limit (0.05 mg/L) to screen large sample sets at environmentally relevant concentrations. The method provides a semi-quantitative composite measurement of similar compounds in an antibiotic family without complex and expensive analytical equipment. r 2004 Elsevier Ltd. All rights reserved. Keywords: Antibiotics; Radioimmunoassay; Monitoring; Wastewater; Water; Method 1. Introduction Antibiotics including tetracyclines (TCs) and sulfona- mides (SAs) are an important group of pharmaceuticals in today’s human and veterinary medicine practice. These compound classes have been widely used for both the prevention and treatment of disease and chlorte- tracycline (CTC) has been used as a feed additive to promote growth in concentrated animal feeding opera- tions (CAFOs) [1]. After application, a fraction of the drugs are completely metabolized to inactive com- pounds, but a significant amount is excreted as active metabolites. Several classes of antibiotics (e.g., TCs, SAs) have been found in hog waste lagoons at concentrations as high as 0.7mg/L [2] and a variety of residual antibiotics have been found in wastewater treatment plant (WWTP) effluents with concentrations as high as 5 mg/L [3,5]. The US Geological Survey measured several classes of antibiotics in water samples from a network of streams across 30 states during 1999 and 2000 [4]. Antibiotic concentrations as high as 1.9 mg/L were found and for the 84–104 streams that were sampled (it varied by ARTICLE IN PRESS *Corresponding author. E-mail address: kcarlson@engr.colostate.edu (K. Carlson). 0043-1354/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2004.04.028